Electrical cutouts are known in the art and are employed in electrical power distribution grids. Electrical cutouts protect power distribution grids from damage due to electrical surges. If an electrical surge occurs within an electrical power distribution grid, an electrical cut out is blown. Accordingly, electrical power is cut-off from the electrical power distribution grid; thereby, protecting the electrical power distribution grid from damage.
An electrical cutout includes a fuse that blows when a surge of electricity is passed through the fuse. When a fuse in fuse cutout is blown, a physical force is exerted on the insulator. As such, the insulators must be able to withstand the force resulting on the blown fuse.
Insulators made from porcelain and ceramic have been designed; however, porcelain and ceramic insulators are heavy and bulky. Further, porcelain and ceramic insulators chip easily and are brittle. U.S. Pat. No. 6,392,526 to Roberts et al. entitled “Fuse Cutout with Mechanical Assist,” the disclosure of which is incorporated herein by reference, illustrates a porcelain insulator and a fuse assembly. As shown in FIG. 1 therein, the fuse assembly 16 is secured to the porcelain insulator by the support members 32 and 34. As depicted in FIGS. 4 and 6 therein, when the fuse is blown, the fuse assembly 16 rotates on the trunnion 24 about pivot point 137 and exerts a force on the porcelain insulator. This force can damage the ridged porcelain insulator thereby resulting in a chipped or weak structure.
Other problems have arisen with electrical cutouts. One such problem occurs when electricity flashes directly from a conducting surface to a grounded surface while the fuse assembly is in the open or closed position. This phenomenon is referred to as “flashover.” The electricity travel gap between the conducting surface and the grounded surface is called the “strike distance.”
Another problem with conventional cutouts occurs when the electrical current travels or “creeps” along the surface of the insulator, bypassing the fuse assembly. “Creep” results when the insulator has an inadequate surface distance. This may occur when water, dirt, debris, salts, air-borne material, and air pollution is trapped at the insulator surface and provide an easier path for the electrical current. This surface distance may also be referred to as the “leakage,” “tracking,” or “creep” distance of a cutout.
Because of these problems, cutouts must be made of many different-sized insulators. Cutouts are made with numerous insulator sizes that provide different strike and creep distances, as determined by operating voltages and environmental conditions. The strike distance in air is known, thus insulators must be made of various sizes in order to increase this distance and match the appropriate size insulator to a particular voltage. Creep distance must also be increased as voltage across the conductor increases so that flashover can be prevented.
Cutouts with plastic or polymeric insulators have been designed; however, such insulators are of complicated design and labor-intensive manufacture. Examples of such cutouts include U.S. Pat. No. 5,300,912 to Tillery et al., entitled “Electrical Cutout for High Voltage Power Lines,” the disclosure of which is incorporated herein by reference. However, Tillery et al. utilizes an injection-molded insulator with a complicated non-solid cross-sectional configuration (Col. 6, II. 20-22) with skirts mounted thereon (Col. 4, II. 53-54).
Therefore, there exists a need for simple design that facilitates ease in the manufacture of the many different-sized cutouts and insulators the electrical power industry requires. There also exists a need for a lighter insulator that allows for greater ease in handling and shipping. Further, there exists a need for an insulator, which will chip or break when a fuse is blown and which can withstand the tension forces exerted by electric power lines.